The invention relates to a method and system for detecting an object caught in the path of an automotive window.
Many of the automotive vehicles today have electronically controlled windows and may even have electronically controlled sun/moon roofs. These systems provide the operator with ease in opening and closing the windows. However, if the operator is distracted while closing the window, it is possible for an object, such as an arm, hand or finger, to be caught between the window and the window frame of the automotive window.
A power window system consists of a regulator coupled to the window and driven by an electric drive motor. The motor typically comprises an output shaft connected to a worm associated with a gear wheel. The gear wheel is connected to an output member coupled to the regulator. Thus, as the motor rotates, the worm rotates, causing the gear wheel to also rotate. Rotation of the gear wheel results in the regulator being driven upward and downward.
One known technique for sensing/detecting the presence of an object caught between a window and its frame when the window is closed utilizes an elastically deformable damper coupled between the gear wheel and the output member. The elastically deformable member permits angular displacement between the wheel and the output member in response to a resistive torque being applied to the output member. The angular displacement is then sensed using a pair of angular position encoders, wherein one encoder is associated with the gear wheel and the other encoder is associated with the output member. If an object is present, a resistive torque is applied to the output member causing the damper to deform and generating an angular displacement between the output member and the gear wheel. This technique, however, has several challenging technical issues concerning the dampers. As examples, the elastic compliance must provide linearity throughout the entire range of torque, the elastic compliance must allow angular displacements large enough to be detected by the encoders, and the elastic stiffness changes as the damper ages.
Thus, there exists a need for a torque sensing device for sensing a torque associated with a resistive force applied to a power window that overcomes the problems encountered by the prior art.
A system for detecting the presence of an object caught between an automotive window and its respective frame is disclosed. The window is mounted on a regulator that is driven upward and downward by an electric drive motor controlled by a control circuit. A sensor is mounted on the drive motor for sensing a resistive torque applied to the regulator. The sensor generates a voltage signal having a value proportional to the sensed resistive torque.
A rotor shaft extends from the drive motor and has a cylindrical worm sleeve encircling it. The worm sleeve is formed with grooves. A grooved gear wheel is associated with the sleeve, and rotates in response to rotation of the worm sleeve. An output member extends from the gear wheel and is coupled to the regulator for moving the window upward and downward. A sensor comprises a piezoelectric layer mounted on the rotor shaft so that it is sandwiched between the worm sleeve and the rotor shaft when the worm sleeve is inserted onto the rotor shaft. The piezoelectric layer senses a pressure in response to the resistive torque being applied to the worm sleeve via the regulator.
Some rotating electric coupling transmits a signal from the piezoelectric layer to a control. In one embodiment, a pair of secondary brushes are mounted on a secondary commutator to transmit the voltage signal generated by the piezoelectric layer. The signal is received by a corresponding pair of secondary contacts connected to the control circuit. The control circuit determines whether or not an object is caught between the window and its respective frame based on the voltage signal. If an object is present, the value of the voltage signal exceeds a predetermined value. In response to this determination, the control circuit either stops or reverses the direction of the drive motor. Other rotating electric couplings may be used.
These and other features of the present invention can be understood from the following specification and drawings.